Corral Victor M, Schultz Eric R, Eisenstein Richard S, Connell Gregory J
Department of Pharmacology, University of Minnesota, Minneapolis, MN 55455, USA.
Department of Nutritional Sciences, University of Wisconsin, Madison, WI 53706, USA.
iScience. 2021 Mar 26;24(4):102360. doi: 10.1016/j.isci.2021.102360. eCollection 2021 Apr 23.
Transferrin receptor-1 (TfR1) has essential iron transport and proposed signal transduction functions. Proper TfR1 regulation is a requirement for hematopoiesis, neurological development, and the homeostasis of tissues including the intestine and muscle, while dysregulation is associated with cancers and immunodeficiency. TfR1 mRNA degradation is highly regulated, but the identity of the degradation activity remains uncertain. Here, we show with gene knockouts and siRNA knockdowns that two Roquin paralogs are major mediators of iron-regulated changes to the steady-state TfR1 mRNA level within four different cell types (HAP1, HUVEC, L-M, and MEF). Roquin is demonstrated to destabilize the TfR1 mRNA, and its activity is fully dependent on three hairpin loops within the TfR1 mRNA 3'-UTR that are essential for iron-regulated instability. We further show in L-M cells that TfR1 mRNA degradation does not require ongoing translation, consistent with Roquin-mediated instability. We conclude that Roquin is a major effector of TfR1 mRNA abundance.
转铁蛋白受体1（TfR1）具有重要的铁转运功能，并被认为具有信号转导功能。TfR1的正常调节是造血、神经发育以及包括肠道和肌肉在内的组织稳态所必需的，而调节异常则与癌症和免疫缺陷相关。TfR1 mRNA的降解受到高度调控，但其降解活性的具体成分仍不确定。在这里，我们通过基因敲除和小干扰RNA（siRNA）敲低实验表明，在四种不同细胞类型（HAP1、人脐静脉内皮细胞（HUVEC）、L-M和小鼠胚胎成纤维细胞（MEF））中，两个Roquin旁系同源物是铁调节稳态TfR1 mRNA水平变化的主要介导因子。实验证明Roquin会使TfR1 mRNA不稳定，并且其活性完全依赖于TfR1 mRNA 3'-非翻译区（UTR）内的三个发夹环，这三个发夹环对于铁调节的不稳定性至关重要。我们在L-M细胞中进一步表明，TfR1 mRNA的降解不需要持续翻译，这与Roquin介导的不稳定性一致。我们得出结论，Roquin是TfR1 mRNA丰度的主要效应因子。
